Tricky probability riddle

[Buccaneer]

You Sir are not right, you are completely right.

The problem is usually missed right here: If the alarm does not ring, he wakes in ............... What most people do is assume that the alarm will not ring only when the Professor remembers to set the clock. There is also another occurance that they forget about and that is of course that the alarm will fail to ring if he forgets to set the clock but there is still a chance that he may or may not wake up in time for class. The Prof will be ontime .06 if he forgets and late .24 if he forgets to set that alarm.

Just like the marbles in the bag problem you have to assume things from the information given but it is easier to define and filter the possible outcomes.

[invast]

Ya.. this is how I got the answer (all laid out)

1) sets alarm -> alarm rings -> makes it to class
2) sets alarm -> alarm rings not -> makes it to class
3) sets alarm not -> alarm rings not -> makes it to class

1) .7 * .8 * .9 = .504
2) .7 * .2 * .2 = .028
3) .3 * 1 * .2 = .06

.504 + .028 + .06 = .592

[MortalWombatDotCom]

[ QUOTE ]
You Sir are not right, you are completely right.

The problem is usually missed right here: If the alarm does not ring, he wakes in ............... What most people do is assume that the alarm will not ring only when the Professor remembers to set the clock. There is also another occurance that they forget about and that is of course that the alarm will fail to ring if he forgets to set the clock but there is still a chance that he may or may not wake up in time for class. The Prof will be ontime .06 if he forgets and late .24 if he forgets to set that alarm.

Just like the marbles in the bag problem you have to assume things from the information given but it is easier to define and filter the possible outcomes.

[/ QUOTE ]

your mode of speech is confusing and so i may actually be agreeing with you here. you do not state what the probability is that the alarm will ring if he does not set it. people seem to be assuming that it's zero, but that's just crazy.